No abstract

Protein kinases (PKs) present in Plasmodium falciparum catalyze phosphorylation reaction to control growth and differentiation of the parasite throughout the life cycle. Protein kinase inhibitors are found to kill the parasite but their cellular target enzymes are not known. Protein kinase inhibitors are evaluated in an in sillico docking studies using plasmodium falciparum RIO-2 kinase (right open reading frame-2 protein kinase) as target enzyme. Most of the protein kinase inhibitors showed appropriate docking within the ATP binding domain of the PfRIO-2 kinase. The initial docking experiments were further validated by a substrate competition experiment to validate the preliminary screening results and test the potentials of these inhibitors under in vivo conditions. Docking and substrate competition study identifies wortmannin, enzastaurin, indirubin-3'-monoxime, apigenin, kaempferol and 8-hydroxy-4-methyl-9-nitro-2H-benzo[g]chromen-2-one as lead inhibitors against native/active form of the PfRIO-2 kinase. The top protein kinase inhibitors bind into the ATP binding site with a similar conformation as ATP. The docking result is in good agreement with the antimalarial schizonticidal IC50 (μg/ml) of an inhibitor and gives a correlation factor (R2) of 0.82 whereas top hit antimalarial inhibitors gives a correlation factor (R2) of 0.99. In summary, our work highlights the importance of PfRIO-2 kinase as a target behind the antimalarial action of protein kinase inhibitors and might help to design a new set of antimalarial remedies.

RIO-2 kinase is known to regulate ribosome biogenesis and other cell cycle events. The 3D model of ATP bound and an unbound form of PFD0975w was generated using AfRIO-2 crystal structure 1TQI, 1ZAO as template employing MODELLER9v7 program. Structural characterization identified Nterminal winged helix domain (1-84), C-terminal kinase domain (148-275), and presence of other critical residues known for ATP binding and kinase activity. Using Q-site and pocket finder, a number of well-defined substrate (peptide) binding regions were identified in the catalytic core of the protein. The peptide binding regions were further validated by molecular modeling a non-specific polyalanine peptide and a sequence-specific peptide2 into these sites to generate a stable PFD0975w/peptide complexes. Peptide fits well into identified pocket on PFD0975w and makes extensive interaction with the protein residues. These newly identified peptide binding sites potentially give opportunity to design a specific inhibitor against PFD0975w. There are subtle but significant differences between Plasmodium falciparum and human RIO-2 to exploit PFD0975w for drug development. In conclusion, our finding will let us to design effective chemotherapy against malaria parasite exploiting PFD0975w as a drug target.

No abstract

Protein kinases (PKs) present in Plasmodium falciparum catalyze phosphorylation reaction to control growth and differentiation of the parasite throughout the life cycle. Protein kinase inhibitors are found to kill the parasite but their cellular target enzymes are not known. Protein kinase inhibitors are evaluated in an in sillico docking studies using plasmodium falciparum RIO-2 kinase (right open reading frame-2 protein kinase) as target enzyme. Most of the protein kinase inhibitors showed appropriate docking within the ATP binding domain of the PfRIO-2 kinase. The initial docking experiments were further validated by a substrate competition experiment to validate the preliminary screening results and test the potentials of these inhibitors under in vivo conditions. Docking and substrate competition study identifies wortmannin, enzastaurin, indirubin-3'-monoxime, apigenin, kaempferol and 8-hydroxy-4-methyl-9-nitro-2H-benzo[g]chromen-2-one as lead inhibitors against native/active form of the PfRIO-2 kinase. The top protein kinase inhibitors bind into the ATP binding site with a similar conformation as ATP. The docking result is in good agreement with the antimalarial schizonticidal IC50 (μg/ml) of an inhibitor and gives a correlation factor (R2) of 0.82 whereas top hit antimalarial inhibitors gives a correlation factor (R2) of 0.99. In summary, our work highlights the importance of PfRIO-2 kinase as a target behind the antimalarial action of protein kinase inhibitors and might help to design a new set of antimalarial remedies.